Procedure for sampling selected field crops

Crop Time to sample Plant part to sample
Corn Some time between emergence and silking/pollination. Do not sample after silks have dried.
  • Seedling stage: All above-ground portion (20 to 30 plants)
  • Prior to tasseling: The entire leaf fully developed below the whorl (15 to 25 plants)
  • Tasseling and shooting to silking: The entire leaf at the ear node (15 to 25 plants)
Corn stalk nitrate-N Samples should be collected at one to three weeks after 80% of the kernels reach black layer stage (physiological maturity) and not after harvest.
  • Six-inch stalk samples should be cut at 6 to 8 inches above the soil surface, at black layer stage, no leaves included.
  • Preferable to sample at least a minimum of 10 stalks from the area of interest.
Soybean The ideal time is when the first bloom appears. However, if problems appear prior to bloom, a sample can be taken. Do not sample after the first pods begin to fill.
  • Seedling stage: All the above-ground portion (20 to 30 plants)
  • Prior to or during flowering: Two or three fully developed trifoliate leaves at the top of the plant (20 to 30 plants)
Small grain Any time before head emerges.
  • Seedling stage: All the above-ground portion (50 to 60 plants)
  • Prior to heading: Select tissue from upper one-third of plant (50 to 60 plants)
Alfalfa and clovers Just prior to bloom (1/10 bloom) or at harvest stage.
  • Take top 6 inches of plant or top 1/3 of plant (40 to 50 plants)
Sorghum Ideal time is when head is fully emerged but before pollination. Samples may be taken at earlier stage if problem develops.
  • Fully expanded and mature leaves (15 to 25 plants)
Cotton Before bolls start to set.
  • The most recently matured leaves (30 to 40 plants)